Study on cracking failure of MLCC body based on mechanical stress

Due to brittle nature for the multilayer ceramic capacitor, it's more prone to bear the excesses of mechanical stress than other electron components used in surface mounting technology. One of the most common causes of ceramic capacitor failures is directly attributable to bending of the printed circuit board after solder attachment. Excessive bending will create mechanical cracks within the ceramic capacitor. The initiation of mechanical micro-cracks, may not cause its failure during the final assembly functional test, however, over time moisture may penetration into the cracks, which can cause a reduction in insulation resistance and eventual dielectric breakdown leading to capacitor failure during operation. In order to in-depth study the cracking mechanism caused by mechanical stress, assembly design and de-paneling design were simulated by means of bending test and simulation. The simulation results show that the contact areas between the external electrode and the solder joint are affected by the stress concentration, which is the weakest part of the ceramic capacitor structure under the bending load. The simulation cloud map of stress concentration is well consistent with the crack path after bending test. In addition, the simulation results indicate that the maximum principal strain of the strain gage unit is approximately linearly changed with time in the process of pushing at a low rate of 0.5mm/min. The article analyzed the cracking failure of multilayer ceramic capacitor under mechanical stress, which provided the methods to improve the ceramic capacitor assembly reliability.